General Knowledge

The burning question

Why do hot things hurt us?

By Khru Sam Bhardwaj of Sam�s Bangkok English Academy, Photograph courtesy of AFP

An object is said to be hot if its temperature is more than our body�s temperature. If we touch such an object, its heat flows into our body and we feel the sensation of heat. Do you know why this happens?

Our body is made up of small cells and these cells are made up of molecules. When molecules

move quickly, they cause heat. So when a hot substance touches our body, the faster-moving molecules of the hot substance increase the motion of the molecules in our own bodies. If this motion is too great, the cells start breaking up, and it is this breaking up of cells that causes a painful sensation. To repair the cells, blood circulation becomes faster in the affected area. That is why the affected part becomes red.

BURNING UP

When the temperature of the object touching the body is very high, a large number of cells and nerves

are destroyed. The heat of the substance also dehydrates the cells of the skin and they break up. This is called burning.

Sometimes substances are so hot that they destroy fat and bones. This causes deeper wounds in the body and the scars caused by such burning are removed by grafting skin taken from other parts of the body.

Burns are classified into four degrees: In first-degree burns, only the upper layers of skin become red. In second-degree burns, deeper layers are damaged and blisters are formed. In third-degree burns, all the layers of the skin are destroyed. In fourth-degree burns not only skin, but tissues beneath the skin are also damaged.

Vocabulary

cell (n): the smallest unit of living matter that can exist on its own; all plants and animals are made up of cells
molecule (n): the smallest unit, usually consisting of a group of atoms, into which a substance can be divided
substance (n): a type of solid, liquid or gas that has particular qualities
repair (v): to mend something that is broken, damaged or torn
nerve (n): any of the long thin threads that carry messages between the brain and parts of the body
dehydrate (v): to remove the water from something
graft (v): to take a piece of skin, bone, etc. from one part of the body and attach it to a damaged part